Certain microstructured optical products, such as described in U.S. 2005/0148725, are commonly referred to as a “brightness enhancing films”. Brightness enhancing films are utilized in many electronic products to increase the brightness of a backlit flat panel display such as a liquid crystal display (LCD) including those used in electroluminescent panels, laptop computer displays, word processors, desktop monitors, televisions, video cameras, as well as automotive and aviation displays.
Brightness enhancing films desirably exhibit specific optical and physical properties including the index of refraction of a brightness enhancing film that is related to the brightness gain (i.e. “gain”) produced. Improved brightness can allow the electronic product to operate more efficiently by using less power to light the display, thereby reducing the power consumption, placing a lower heat load on its components, and extending the lifetime of the product.
Brightness enhancing films have been prepared from polymerizable resin compositions comprising high index of refraction monomers that are cured or polymerized. Halogenated (e.g. brominated) monomers or oligomers are often employed to attain refractive indices of for example 1.56 or greater. Another way to attain high refractive index compositions is to employ a polymerizable composition that comprises high refractive index nanoparticles.
One common monomer that has been employed as a reactive diluent in polymerizable resin compositions is phenoxyethyl acrylate, having a refractive index of 1.517 and a viscosity of 12 cps at 25° C.
Other monomers for use in microstructured optical films have been described in U.S. Publication Nos. US2010/0048802, US2009/0275720, and US2009/0270576.